Question

A young hockey player stands at rest on the ice holding a 1.2-kg helmet. The player tosses the helmet directly in front of him with a speed of 7.0 m/s and recoils with a speed of 0.30 m/s .

Find the mass of the hockey player.

Answer 1

`M_p = 28 kg`

Step-by-step explanation:

For answer this we will use the law of the conservation of the linear momentum P:

`P_i = P_f`

so:

0 =
`M_cV_c + M_pV_p`

where
`M_c` is the mass of the helmet,
`V_c` is the velocity of the helmet,
`M_p` is the mass of the hockey player and
`V_p` is the velocity of the hockey player after launch his helmet.

note: we will take the direction of the helmet like positive.

Replacing values, we get:

0 =
`(1.2 kg)(7m/s) + M_p(-0.3m/s)`

Solving for
`M_p`:

`M_p = 28 kg`